Anesthesia in all patients was based on fentanyl, midazolam, vecuronium and sevoflurane. The depth of anesthesia was monitored using bispectral index (BIS). During cardiopulmonary bypass alpha-stat technique was used with the maintenance of normothermia (35.5-36.5°C) or spontaneous hypothermia (up to 32°C). With the off-pump technique, the core temperature was maintained between 36 and 37°C. Surgical technique was standardized. Routine hemodynamic monitoring was performed throughout the surgery and continued on the first postoperative day. Plasma levels of S100β protein were determined 6 h and 30 h following the end of on-pump surgery, and 3 h following the end of off-pump surgery. C reactive protein levels and other routine laboratory parameters were measured from blood samples collected 1 h, 4 h and 12 h postoperatively. On the first postoperative day blood samples were collected at 08:00 AM to determine cortisol levels, C reactive protein and other routine laboratory parameters, and cortisol was also measured on the same day at 04:00 PM, and 12:00 AM. C reactive protein and other routine laboratory parameters were repeatedly measured at 08:00 AM on the following postoperative days, except for cortisol levels which were measured on postoperative days 3 and 5. Registered nurse carried out the standardized test (Delirium Observation Screening Scale (DOS) scale) to assess the patients for the development of postoperative delirium from second to fifth postoperative day (at 07:00 AM, 02:00 PM and 10:00 PM).